Vapor
by Quirkless Wannabe
Summary: With no other options left, the principal hires a Private Investigator to uncover UA's security leak. However, the PI will only work the case on the condition that an unknown quirkless girl be transferred into the Hero Course. Who is she, and will Class 2-A welcome her into their family? Will the traitor be caught before an unseen evil destroys UA beyond repair?


Prologue

It was noon on a Sunday about a month before the end of the school year, and Aizawa Shouta wanted nothing more than to be back in his bed. _The faculty meeting ended 30 minutes ago,_ he thought exasperatedly from the comfort of his yellow sleeping bag. _Why are the seven of us still here?_

As if he had suddenly developed a mind-reading quirk, UA's Principal Nezu wrapped up the _thrilling_ conversation on pedagogy he had been having with Thirteen and addressed all of the teachers he had asked to stay behind. Aizawa unzipped the sleeping bag to his shoulders and sat up in his chair.

"I've asked you seven to stay because there is a serious matter that needs to be addressed before the next year's classes begin." Principal Nezu looked solemnly across the conference room at his staff. "We are about to begin a new school year, and we are still unable to identify the security leak within our school. It's been months since villains attacked UA, but it would be unwise to assume the danger is over. In fact, since things have been so quiet of late, I believe now is the time to be vigilant."

"That is true." Vlad looked gravely at his colleagues as he spoke. "An attack could be imminent and we would have no way of knowing. Even with our added security measures, we're little more than sitting ducks."

"I'm just not sure what else we can do at this point," said Ectoplasm from his seat between Vlad and Thirteen. "We've thoroughly investigated the situation, especially since moving the students into the dorms, and even with the help of the police, nothing has turned up."

"Well, that's what I'd like to discuss. I know the safety of our students is the highest priority of everyone in this room, so please understand that I would not resort to this if I didn't think it was necessary. That said, I've decided to bring in outside help."

Aizawa and Present Mic shared a glance before turning back to Principal Nezu. "You're bringing in outside help, besides the police?" the Voice Hero asked.

"I thought we wanted this to be handled quietly, Principal," Aizawa drawled, donning the most unimpressed expression he could muster and directing it at his tiny, furry boss. His sleeping bag was entirely unzipped and off his body now. He wasn't exactly sure what the small creature was planning, but he was fairly certain he was not going to like it. _It's way too early for this_ , he thought to himself.

Nezu gave the Erasure Hero a knowing smile. "I assure you, it _will_ be handled quietly," he responded before turning to address the rest of the teachers. "I've decided to hire Smoke."

A heavy silence fell over the room as the teachers shared their looks of disbelief across the table.

Thirteen was the first to speak after several tense seconds, leaning forward in their seat to make sure the principal was being serious. "You're sure this is necessary, sir?"

"I believe so. You have reservations?"

"Honestly, Principal, I'm a little surprised you don't," Midnight respectfully asserted. She gave the Space Hero a supportive nod from across the table before turning back to her boss. "I mean, don't get me wrong, a man shrouded in mystery is definitely a turn-on," she continued, trying to break up the tension in the room with her signature smirk, "but to give someone like Smoke full access to UA? No one knows anything about him at all."

"That's not exactly true, though, is it?" Snipe interjected. "We know his track record is impeccable. He's never failed to solve a case he's taken on. A bullseye every time."

"But that in itself doesn't seem suspicious? Everybody fails sometimes, especially in such a risky line of work."

"Not to mention, he's rarely ever seen in person, so no one can really say for certain what he looks like."

"I have met with him in person."

Another hush fell over the room as everyone turned to look at the principal.

"I happen to be one of the few who knows who he is. Unfortunately, I can't say much about it—you know how American heroes are about their secret identities—but I really trust him, and think his help is crucial to this investigation and to keep our students safe. I'm asking you all to trust me in this decision. Will you?"

Nezu's bright eyes shone with his trademark enthusiasm, but hidden beneath the surface was a kind of smugness that said, _You all know I'm several steps ahead of you, so you're going to go along with my choice whether you want to or not_. He made eye contact with every teacher at the conference table until he was finally met with a reluctant chorus of nods.

"Excellent!" He clapped his paws together and smiled brightly. "Now, our friend has given us two conditions that we must meet if he is to find our leak." The teachers glanced at each other with raised eyebrows at their boss's use of the word "friend."

"The first condition," Nezu continued, "is that classes A and B of our hero course must stay as they are moving into the new year. This means that all the students of last year's class 1-A will be in class 2-A together this year, and the same is true for the students of class 1-B—well, now 2-B, I suppose."

Aizawa and Vlad looked at each other across the table. "Will the teachers be moving forward with their students as well?" the Blood Hero asked.

"Yes, that's right. You and Eraserhead will be acting as second-year homeroom teachers this year, moving ahead with your respective classes. Present Mic and Ectoplasm will be taking care of our incoming first-years, and Midnight and Snipe will continue teaching the third-years."

Present Mic held back a sigh as he watched his best friend's brow furrow in annoyance. _I should probably say something cool before Shouta blows a gasket._ "Oh, so those two classes will remain exactly the same!" he yelled dramatically before swinging his lanky arm around his irritated friend's shoulders. "Awwww, Shouta looks grumpy, but we all know you have a soft spot for these kiddos! It'll be nice to have no change for a change, yeeeeah?!"

"Actually, there will be one significant alteration to both classes," Principal Nezu said, his smile never faltering.

"Oh? And what's that?" Aizawa quipped snarkily before Mic had the chance to make more noise. _Still too early._

"Each hero class will be taking on an additional student. That makes 21 students in each class."

For the umpteenth time that morning, the teachers stared at the principal with varying degrees of confusion and disbelief. "I'm sorry?" Vlad asked. "What exactly is the reason for this change? Is this Smoke's second condition?"

"This part was my idea, to maintain balance!" the small creature continued, as if this was business as usual. "The two new second-year students have already been decided. Joining class B will be Shinsou Hitoshi, the General Studies student who performed so well in the Sports Festival last year. That shouldn't come as a surprise, he applied for the transfer some time ago and has been training hard all semester."

"And joining class A?" Aizawa looked tiredly at his boss, expecting the worst.

"Ah, yes. That is Smoke's other condition. Here." The principal gave Aizawa a placating smile and handed him a folder. "We must transfer this young lady, Arisa MacArthur, into our hero course as a second-year. Try not to expel her right away, Shouta-kun."

Mic leaned forward and let out a nervous laugh as he read over the Erasure Hero's shoulder:

NAME: ARISA MACARTHUR

AGE: 16 YEARS

QUIRK: NONE

Aizawa's eyes widened ever so slightly, then rose defiantly to meet the principal's gaze.

"This isn't going to work."

Three weeks later, a young girl with tanned skin and untamed, apple-red hair stared down the enormous front gates of UA. She breathed steadily as she took a moment to survey the vast, empty campus from the outside.

"Well, Dad," she muttered with a dry smile, "This place already feels like an alien planet to me."

 _Can't wait to tell you about it, though_ , she thought. _I'll be sure to make you proud._

With that thought in mind, Arisa MacArthur adjusted the large black bookbag on her shoulder, gripped the handles of a cart stacked with two large cardboard boxes full of her belongings, and warily made her way towards the dorm building for UA Hero Course Class 2-A.


End file.
